This article or section is in need of attention from an expert on the subject. Please help recruit one or improve this article yourself. See the talk page for details. Please consider using {{Expert-subject}} to associate this request with a WikiProject

Abscisic acid
Chemical name	[S-(Z,E)]-5-(1-Hydroxy-2,6,6-trimethyl- 4-oxo-2-cyclohexen-1-yl)-3-methyl- 2,4-pentanedienoic acid[1] Image File history File links Information. ... Image File history File links Abscisic_acid_structure. ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ...
Chemical formula	C15H20O4
Molecular mass	264.32 g/mol
CAS number	[14375-45-2]
Density	? g/cm³
Melting point	161–163 °C
Boiling point	120 °C (sublimes)
SMILES	O=C1CC(C)(C)C(O)(/C=C/C(C)=CC(O)=O)C(C)=C1
Disclaimer and references

Abscisic Acid (ABA), also known as abscisin II and dormin, is a plant hormone. It was once thought to be pivotal in abscission and in bud dormancy.^[2] Currently, the hormone is thought to act mainly to inhibit growth, to be perhaps only one of the hormones involved in bud dormancy and not the one involved in enforcing it throughout the winter, and help the plant tolerate stressful conditions, particularly water stress. This article or section does not cite any references or sources. ... The molecular mass (abbreviated Mr) of a substance, formerly also called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg V is... The melting point of a crystalline solid is the temperature at which it changes state from solid to liquid. ... Italic text This article is about the boiling point of liquids. ... The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings. ... Plant hormones (or plant growth regulators, or PGRs) are internally-secreted chemicals in plants that are used for regulating the plants growth. ... Abscission (from ab- away from, and scission cutting or severing) is the shedding of a body part. ... Dormancy is a arrested plant growth. ...

As indicated, Abscisic acid is named so because it was once believed that this plant growth regulator caused the abscission of leaves from deciduous trees in the fall. This is the complete opposite of what auxin, gibberellins, and cytokinins, does to the leaves as they all inhibit leaf senescence and abscission. However the plant hormone Ethylene, also causes leaves to abscise, and the latter is now considered to be more important in the regulation of leaf senescence, but ABA may still be involve in the final break away of the leaf. Deciduous means temporary or tending to fall off (deriving from the Latin word decidere, to fall off) and is typically used in reference to trees or shrubs that lose their leaves seasonally. ... IAA appears to be the most active Auxin in plant growth. ... Gibberellins are plant growth substances (phytohormones) involved in promotion of stem elongation, mobilisation of food reserves in seeds and other processes. ... Zeatin is named after the genera of corn, Zea as it was first discovered in corn. ...

In terms of preparing for Winter, abscisic acid is produced in terminal buds. This slows growth and directs leaf primordia to develops scales to protect the dormant buds during the cold season. The plant growth regulator also inhibits the division of cells in the vascular cambium, preparing for winter by suspending primary and secondary growth. Vascular cambium is a tissue found in the stems of perennial dicots. ...

Abscisic acid is produced in the roots in response to decreased soil water potential. It travels to the leaves where it has a rapid effect altering the osmotic potential of guard cells of leaves, causing them to collapse and stomata to close. This prevents transpiration from occurring and prevents further water loss from the leaves in times of low water availability.

Location, Characteristics and Occasions for Synthesis Induction

• Released during desiccation (of vegetative tissues)
• Synthesized in green fruit and seeds at the beginning of the wintering period
• Moved within the leaf and can be transferred to the leaf from the roots by the transpiration stream
• Rapidly-translocated
• Produced in response to stress, such as heat stress, water stress, salt stress etc.
• Synthesized in all plant parts, e.g. roots, flowers, leaves and stems

For other uses, see Fruit (disambiguation). ... A ripe red jalapeño cut open to show the seeds For other uses, see Seed (disambiguation). ... “Foliage” redirects here. ... In medical terms, stress is the disruption of homeostasis through physical or psychological stimuli. ... Stem showing internode and nodes plus leaf petiole and new stem rising from node. ...

Effects

• Stimulates stomatal closure, in order to reduce transpiration and prevent water loss.
• Inhibits fruit ripening
• Encourages seed dormancy by inhibiting cell growth – inhibits seed germination
• Inhibits the uptake of Kinetin
• Activates the pathogen resistance response defense
• Induces senescence in already-damaged cells and their proximate neighbours (speculative)
• Quickly puts a plant, organ, tissue or individual cell in a defensive posture (whatever this entails) in response to rapidly-developing nutrient or environmental stress that threatens their survival (speculative)
• Engorges the embryo of seed until broken down by water or low temperatures.

References

1. ^ Abscisic Acid Chemical Name
2. ^ Plant Physiology: Abscisic acid